Influence of the delay between the prepulse and the main discharge on the characteristics of an electric-discharge HgBr laser with ultraviolet preionization

An experimental study was made of an electric-discharge HgBr laser operated in a system with a high-voltage prepulse applied to the electrodes following a preionization pulse. The laser active volume (3 X 4 X 90 cm) was preionized by a mesh cathode using radiation from a creeping discharge on a glass surface. The mixture consisted of Ne with N₂ (2%) at a total pressure of 3 atm (room temperature) and HgBr₂ vapor at a concentration of around 3 X 10¹⁶ cm ^{– 3}. The laser pulse energy depended strongly on the delay τ between the prepulse and the main discharge, reaching a maximum at τ ≈ 1 μs. It was found that the mesh electrode created small-scale (~ 1 mm) inhomogeneities of the conductivity in the discharge zone. The introduction of a delay between the prepulse and the main discharge "eroded" these inhomogeneities, thus increasing the active volume and the lasing energy. An output pulse energy of 0.9 J was obtained with an efficiency of 0.4%.